THE COOK'S OR HARVEY ISLANDS. 405 



Not uncommon on the ground in forests at Earotonga, and as near as I can 

 ascertain is peculiar to that island. When Mr. Pease first described it he gave 

 "Atiu" as its habitat; but in his List of Polynesian l^and Shells he correctly 

 refers it to Rarotonga. 



It can readily be distinguished by its smooth rounded whorls. 



GENUS OMPHALOTROPIS, Pfeiffer. 

 O. OCHROSTOMA, Pease. 

 Bealia ochrostoma, Pease, Amer. Jour. Conch., 1865, p. 281; 1866, p. 82, PI. 5, fig. 1. Martens 



& Langk., Don. Bism., p. 59, PI. 3, fig. 19. Pfeiffer, Mon. Pueum., Suppl. 3, p. 224. 

 Omphalotropis ochrostoma, Pease, Jour, de Conch., 1869, p. 141. Schmeltz, Cat. Mus. Godeff., 



v., p. 101. 

 OmphalotTopis ochroleuca, "Pease," Paetel, Cat. Conch., p. 124. 

 Atropis ochrostoma^ Pease, Proc. Zool. Soc, 1811, p. 416. 

 Hydr^ocena ochrostoma, Paetel, Cat. Conch., p. 124. 



I gathered hundreds of examples of this species in the low-land forests of 

 Aitutaki. 



Though referred by Pease to his subgenus Atropis^ the base, nevertheless, 

 exhibits a rather conspicuous keel, and very rarely with a periphery carination. 

 The vertical aperture is more frequently white than ochraceous. The whorls, 

 which are separated by a deep suture, vary from five to six. Adults are decorti- 

 cated and usually more or less eroded. They show considerable variation in color; 

 white, corneous, pale luteous, and ruddy-brown. 



0. VARIABILIS, Pease. 



Bealia variabilis, Pease, Amer. Jour. Conch., 1865, p. 288; 1866, p. 82, PI. 5, fig. 2. Martens & 



Langk., Don. Bism., p. 59, PI. 3, fig. 18. Pfeiffer, Mon. Pneum., Suppl. 3, p. 221. 

 Omphalotropis variabilis, Pease, Jour, de Conch., 1869, p. 124; Proc. Zool. Soc, 1811, p. 416. 



Paetel, Cat. Conch., p. 124. Schmeltz, Cat. Mus. Godeff., v., p. 101. 



This species is probably distributed throughout the group. I obtained it in 

 abundance at all the islands I explored. 



It may be distinguished from the preceding by its less variable color, more 

 produced spire, more conspicuous basal keel, and the constant carination on the 

 periphery. Though decorticated it is never eroded, and the surface is smoother, 

 more shining, and the suture is more deeply incised. The vertical aperture is 

 always whitish. Whorls six. 



0. OVATA, Pease. 



Hydrocena ovata, Pease, Proc. Zool. Soc, 1864, p. 614. 



Omphalotropis ovata, Pease, Jour, de Conch., 1869, p. 148; Proc. Zool. Soc, 1811, p. 416. 



Bealia ovaia, Pfeiffer, Mon. Pneum., Suppl. 3, p. 212. 



